The following United States patents are known by applicant to be pertinent to the present invention:
______________________________________ 3,848,232 3,623,068 3,827,041 3,593,316 3,803,584 3,582,936 3,772,676 3,396,377 3,641,555 3,389,404 3,624,633 3,346,853 ______________________________________
In the prior art, as exemplified by the patents cited in the foregoing, it is know to provide a video display device with a random access memory which stores digital codes representative of strings of text characters and define the manner and position in which they are to be displayed on a cathode ray tube output device. Usually there is mapping circuitry and display generation associated with the RAM which converts the memory contents of the RAM into alpha-numeric display characters, and which uses the display commands from the RAM to position the alpha-numeric characters on the display screen.
Usually the circuitry is arranged so that display of strings of text characters occurs in fixed sequences, one line following another. This takes the display format out of the hands of the computer operator. In many situations, this is the most efficient form of information display.
In some circumstances it would be more advantageous for the computer operator to have more control over the display format. For example, in text editing, information retrieval, and error checking of incoming data, it would be beneficial to permit the computer operator to control the display format. That is, the computer operator could select not only the address of the memory contents to be displayed, but also the format in which the data appears on the display screen.
These control functions may best be provided in a video display module which is distinct from the central processing unit, so that the program may run undisturbed while information is retrieved by the operator from the RAM of the display module itself. This arrangement would consume less computing time of the contral processor.